Tungiasis is a parasitic disease caused by fleas. Pathognomonic symptoms are the presence of extensive inflammatory infiltrate at the site of introduction of the pathogen, severe itching and pain. Often the disease is accompanied by impaired walking function, edema of the lower extremities and fever. Diagnostics is based on the detection of flea eggs, insects themselves, for this surgical excision and microscopic examination of tissues are often necessary. Etiotropic treatment has not been developed; therapy is reduced to the removal of the parasite, pathogenetic and symptomatic effects on the body.
B88.1 Tungiasis [infestation by tropical sand flea]
Tungiasis (sarcopsillosis, sand flea disease) refers to dermatophiliasis associated with the introduction of insects into the skin and the sensitizing effect of their saliva. The first written mention of pathology is found in the records of the Columbus expedition, although the pathogen itself was discovered only at the end of the twentieth century. The disease is endemic to countries such as Brazil, Trinidad, Tobago, Sri Lanka, China, Ecuador, Peru, Madagascar and several African republics. The seasonality of nosology is associated with the activity of pathogens, the peak is in July-October. In endemic areas, up to 50-80% of the population is affected. Children and men are most often infected.
The causative agents of the disease are female sand fleas of the genus Tunga, more often Tunga penetrans (Sarcopsylla penetrans). Domestic animals (goats, cows, pigs, cats, dogs) serve as reservoirs for them. The incidence of goat livestock correlates with the number of cases of human tungiasis, especially in sub-Saharan African countries. The most susceptible to infection are young goats, whose main symptoms of the disease are necrosis of hoof tissues, lameness, cough. The path of infection is contact. About 97% of lesions are localized on the soles of the feet.
The main risk factors for tungiasis are living in unfavorable social conditions, working with animals, soil. It is believed that elderly and disabled people, due to reduced mobility, deterioration of visual acuity, solitary living, are more susceptible to infection. Mental disorders, trypanosomiasis, alcoholism, Klippel-Trenone syndrome are considered medical factors predisposing to prolonged contact with the earth and severe course of tungiasis. With a decrease in the sensitivity of the skin (leprosy, diabetic neuropathy), the risk of infection also increases.
The fertilized female insect penetrates deep into the epidermis due to the properties of its saliva. Erythema occurs at the site of introduction, edema increases as the parasite grows, and inflammatory infiltration occurs. Inside the skin, the pathogen causes such phenomena as hyperkeratosis, parakeratosis, acanthosis, hypergranulosis, spongiosis and papillomatosis. Often hemorrhagic tissue impregnation. After 5-6 days, the eggs inside the pathogen mature, come out through the abdominal end of the flea left free. After the rejection of the eggs, the female dies. After 2-4 days, larvae emerge from the egg, which go through 2 stages of growth, and then turn into pupae. Insects become mature adults within 11 days.
The incubation period of tungiasis is 8-12 days. At the beginning of the infection, during the introduction of the insect into the skin, unpleasant sensations are possible in the area of fleas, which the patient may practically not notice. Body temperature usually remains within normal values; fever symptoms indicate the addition of a purulent flora. A further increase in the size of the parasite causes a feeling of bursting, pain, itching, the affected area becomes painful, red, swollen. In the center there is a bump or bubble with a black dot center.
The most frequent localizations of tungiasis are the periarticular areas of the soles, palms, however, affects can be on the back of the head, wrists, back, hips, abdomen, pubis. The number of inflammatory foci can vary from 5 to 30 or more. The more massive the invasion, the more severe this infection is. When the lower extremities are affected, patients often experience severe pain, which increases when walking and at night, they have to restrict movement, take a forced pose. Symptoms of swelling of the foot and lower leg are often added.
Common complications of tungiasis are secondary purulent infections that occur due to skin cracks, swelling of the periarticular rollers, followed by the formation of ulcers and scars, less often sepsis. With prolonged absence of treatment, deformities of the nails and lower extremities occur. The big problem of the transferred tungiasis is considered to be lymphostasis, reaching the elephantiasis of the lower extremities. The ease of occurrence of recurrent tungiasis in persistent unsatisfactory living conditions leads to prolonged immobilization, chronic stress disorder, depressive symptoms, and stigmatization of patients.
Timely detection and treatment of symptoms of tungiasis is a problem of modern clinical infectology, requires examination by an experienced infectious disease specialist. A thorough collection of epidemiological anamnesis is required, clarification of living conditions when staying in areas with a high prevalence of infection. According to clinical indications, dermatovenerologists and parasitologists are often involved. The basic laboratory and instrumental diagnostic signs of tungiasis are:
- Physical data. In the area of the feet, periarticular rollers, interdigital spaces, a papule or vesicle with a dark dot in the center is found on the soles, when squeezed, eggs, parts of fleas come out. Multiple lesions are possible. With purulent complications in the area of the entrance gate, fluctuation is possible. Internal organs are usually without pathology.
- Laboratory tests. There are no specific changes in blood and urine tests. With a general clinical study, it is possible to detect leukocytosis, moderate anemia, eosinophilia, acceleration of ESR. Hypoproteinemia, increased activity of ALT, AST are determined only with severe allergies and severe course.
- Detection of infectious agents. To identify the parasite, microscopy of the separated infiltrate or biopsy is necessary, for the purpose of differential diagnosis, culture media is seeded. During surgical excision, pathohistological material is examined. Serological and PCR diagnostics are not used.
- Instrumental techniques. Radiography of the extremities allows to exclude bone destruction by the type of osteomyelitis with fistula passages. Ultrasound examination of soft tissues and bones aims not only at differential diagnosis, but also at timely detection of symptoms of localized and diffuse purulent processes.
Differential diagnosis is carried out with paronychia, folliculitis of bacterial nature, which usually occur after injuries, cuts, abrasions; miasis, a characteristic feature of which is the rapid movement of the fly larva (up to 30-40 cm per day); schistosomiasis with its local skin edema and urticaria. Scabies is manifested by white-gray lines with a black dot at one end, changes are localized in the interdigital spaces, on the wrists, forearms, on the penis. Stinging ant bites look like vesicular-pustular elements against the background of hyperemic skin and pronounced itching.
Patients with single lesions, moderate and mild course of parasitosis can be treated on an outpatient basis. Patients with complications, symptoms of decompensation of chronic pathologies should be hospitalized. The diet is standard, it is recommended to increase the amount of protein food, the consumption of boiled water. Strict observance of personal hygiene is important, it is allowed to apply a sterile bandage to the affected area, treatment with antiseptic solutions when changing the dressing. With severe pain, as well as for the prevention of symptoms of lymphostasis, it is necessary to ensure rest and an elevated position of the affected limb.
Standard protocols for the treatment of invasion have not been developed. The most frequent choice is the use of local remedies after the removal of the pathogen. Previously recommended exposure of the limb in a solution of potassium permanganate for 10 minutes has low effectiveness, and also carries the risk of skin burns. Sometimes vaseline and other ointments are used to inactivate fleas, to facilitate its elimination. The most common treatment of symptoms of this parasitosis includes:
- Etiotropic agents. There is no effective chemotherapy, the most commonly used drugs include tiabendazole, albendazole, and ivermectin, but their oral use is permissible only in cases of multiple sand flea lesions. There are recommendations for taking trimethoprim.
- Pathogenetic therapy. Treatment of tungiasis is impossible without relief of inflammatory phenomena, up to the use of infusion detoxification agents, antihistamines, in severe cases – systemic glucocorticosteroids. An important measure is high-quality anesthesia of patients, sometimes with the use of opioid analgesics.
- Symptomatic medications. This group includes improving venous outflow, decongestants, desensitizing, antipruritic and antibacterial agents, as well as angioprotectors. Antibiotics are allowed to be used only in the case of a proven bacterial complication, injectable penicillins, cephalosporins, macrolides are most often used.
The main method of insect elimination is surgical excision of the infiltrate or removal of the pathogen with a needle, curette. At the same time, it is important to observe the rules of asepsis and antiseptics, which is especially important for residents of endemic zones, where such manipulations are carried out with non-sterile and often improvised means such as needles, spikes, pins and carry a high probability of infection with HIV, hepatitis B and C viruses, syphilis, and other hemocontact infections. After opening, the wound is treated with alcohol for additional inactivation of the flea, a non-sterile bandage is applied. Patients with symptoms of tungiasis should receive tetanus prophylaxis.
Local application of a mixture of two-component dimethicone is effective: when used for 2 days, only 7% of parasites remained alive, after one week of regular use, 95% of fleas lost viability, inflammatory symptoms were reduced, healing occurred without rough scars. The difficulties lie in calculating the dose of the drug – the thicker the stratum corneum of the epithelium, the longer the exposure of the drug and the greater its concentration should be. Some studies recommend the use of repellents containing aloe vera extract and coconut oil, jojoba ‒ their pronounced anti-inflammatory effect has been revealed in the symptoms of tungiasis.
Prognosis and prevention
The prognosis with timely detection and treatment of invasion is favorable. The mortality rate is less than 1%, associated with the addition of symptoms of purulent complications. No vaccine has been developed at the moment. The main measures of disease prevention are called insecticidal tillage in endemic zones, wearing closed shoes, socks, protective clothing. It is necessary to exclude the contact of bare areas of the body and the ground, be sure to wash your feet after walking. It is important to observe the hygiene of the home, including plastering the walls, cementing the floor, regular wet cleaning.